1. Field of the Invention
The present invention relates to a process for blending and distributing a slurry solution to a point of use in a semiconductor processing facility. The invention also relates to a system and process for producing and distributing suspensions and slurries, particularly abrasive slurries employed in the electronics industry.
2. Description of Related Art
In the semiconductor manufacturing industry, chemical mechanical polishing or planarization (CMP) is used to planarize the surface of a semiconductor substrate. Typically, the CMP process involves attaching a semiconductor wafer to a carrier via a mounting pad, and to polish the exposed surface of the wafer by bringing it into contact with a polishing pad. The mechanical abrasion between the wafer surface and the polishing pad results in planarization of the wafer surface.
To aid in the planarization of the wafer surface and to transport disengaged wafer particles from the wafer surface, a slurry is introduced between the wafer surface and the polishing pad. Slurries typically include abrasive particles and a medium in which the abrasive particles are suspended. In addition, oxidizing agents are often blended with the slurry either at the point of use or on-site as per customer specifications. Surfactants can also be added to the slurry to enhance the wettability of the surface being polished and reduce vibrations during planarization. The chemical components of the slurry react with the wafer surface, thereby making the wafer more easily polishable.
One common use of these techniques is the plug formation process. In this process, after depositing a dielectric layer on the semiconductor surface, contact holes are formed in the dielectric layer by photolithography and etching processes. A metal is then blanket deposited on the wafer to fill the holes and to form an overlying layer of the metal. The CMP process is next performed until the metal over the dielectric layer is removed, leaving metal plugs in the holes.
There are several problems associated with the mixing and handling of slurries. For example, while deionized water is generally available in semiconductor manufacturing environments, the other slurry components are generally hazardous chemicals which must be carefully handled, mixed and delivered to the process tool. In addition, these slurries are colloidal suspensions which must remain homogeneous after mixing and during distribution to the point of use. Further, typically slurries have a limited shelf life after being mixed.
Slurry delivery and mixing systems have been proposed in which the slurry is mixed on site at a manufacturing plant. An example of such a system is disclosed in U.S. Pat. No. 5,407,526 to Danielson et al, wherein a slurry concentrate and oxidant are pumped into a mixing chamber where they are mixed to form a slurry which is delivered to the processing tool. In this system, the mixing of slurry can occur only when the tool is in operation.
Another slurry mixing system is disclosed in U.S. Pat. No. 5,478,435 to Murphy et al, in which slurries are pumped directly onto a polishing pad of a chemical mechanical planarization tool. The slurry components are blended until a desired pH is obtained. However, upon delivery to the processing tool, the solution is not necessarily homogeneous or of the desired concentration for the particular application.
To meet the requirements of the semiconductor processing industry and to overcome the disadvantages of the related art, it is an object of the present invention to provide a novel, integrated system for onsite blending and distribution of an oxide abrasive slurry solution.
It is another object of the invention to provide the slurry solution constituents to a blending tank based on weight and/or optionally by injection, or together with the metering pump filling by weight.
It is a further object of the invention to monitor and adjust the concentration of the components forming the slurry solution.
It is another object of the invention to supply a homogeneous slurry solution to a number of processing tools regardless of whether they are in operation.
It is yet another object of the invention to continuously supply the processing tools while simultaneously formulating a subsequent slurry solution to be supplied to the process tank and therefrom to the processing tools.
It is another object of the invention to provide a facile manner of accessing different parts of the system to clean or repair them while minimizing down time.
Other objects and aspects of the present invention will become apparent to one of ordinary skill in the art upon review of the specification, drawings and claims appended hereto.
In accordance with the present invention, an innovative process and system for blending and distributing oxide abrasive slurry solutions is provided. The invention finds particular applicability in the semiconductor manufacturing industry, wherein chemical solutions of desired formulations can be generated on-site, with the resulting solution being introduced directly into one or more semiconductor processing tools for chemical mechanical polishing.
According to an aspect of the invention, a process for blending and distributing a slurry solution to a point of use is provided. The process includes supplying at least a first and a second component to a mix tank sequentially. Each component is added until a coarse weight set point is reached and, upon attaining said coarse point, the component is allowed to settle and further added via pulsed injection until a fine weight set point is attained. Thereafter, the components are blended into a slurry solution and conveyed to a process tank and henceforth to the point of use.
According to another aspect of the invention, a system for blending and distributing a slurry solution to a point of use in a semiconductor facility is provided. The system includes a mix tank wherein at least a first and second component are added sequentially until each component reaches a coarse weight set point. The component is allowed to settle and further added via pulsed injection until a fine weight set point is attained. A stirrer is employed for blending the at least first and second component into a solution, and a process tank is provided for receiving the solution and distributing it to the point of use.